Methods of functionalizing reclaimed elastomer material and compositions comprising the same

ABSTRACT

A method of functionalizing reclaimed elastomer material is described. The method involves subjecting particles of the reclaimed elastomer material to shear at temperatures less than 100° C. such that inter-chain bonds of the reclaimed elastomer material are cleaved wherein the particles of the reclaimed elastomer material have a size of 60 mesh or smaller. The reclaimed elastomer material can be subjected to shear in the presence of a modifier which selectively promotes the cleavage of inter-chain bonds in the reclaimed elastomer material. A functionalized reclaimed elastomer material made by a method as described above and an elastomer compound which comprises the functionalized reclaimed elastomer material are also described.

This application is a divisional application of, and claims the benefitof and priority to, U.S. patent application Ser. No. 14/070,046, filedon Nov. 1, 2013, entitled “METHODS OF FUNCTIONALIZING RECLAIMEDELASTOMER MATERIAL AND COMPOSITIONS COMPRISING THE SAME”, which claimsthe benefit of and priority to, U.S. Provisional Patent Application No.61/721,907, filed Nov. 2, 2012, entitled “Elastomeric CompositionsComprising Functionalized Reclaimed Elastomer Particles”, both of whichare incorporated herein by reference in their entireties.

TECHNICAL FIELD

The present disclosure relates generally to methods of using reclaimedcross-linked elastomer material and, in particular, to methods offunctionalizing reclaimed elastomer materials such as micronized rubberpowder and to elastomer compounds and compositions comprising thefunctionalized elastomer materials.

BACKGROUND

Reclaimed elastomer materials (i.e., “reclaimed materials,” “ground tirerubber,” “GTR,” “micronized rubber powders,” or “MRP”), which includevulcanized elastomer materials, are used in a variety of applications,including elastomer compositions (e.g., tire tread compounds for vehicletires), plastics compositions (e.g., as fillers for polyolefins),asphalt fillers, and others. In many of these applications, themicronized rubber powders are used as “filler” in place of a portion ofthe virgin compound material. One of the primary reasons for the use ofreclaimed elastomer materials is cost. Moreover, rubber powders, whetherGTR or MRP, are typically significantly less expensive than virgin(i.e., non-reclaimed) rubber or plastic, and when used as a “filler” inelastomer or plastic compositions, tends to reduce the overallmanufacturing cost of the composition. Further, because micronizedrubber powders typically are made from recycled or reclaimed material(e.g., vulcanized scrap from manufacturing processes and used tires orother elastomeric products), reincorporating them into elastomer andplastic compositions reduces landfill waste and results in a moreenvironmentally-friendly product. Finally, use of recycled GTR or MRPprovides a strategic supply chain hedge against petroleum-based supplychain price and supply volatility.

Generally, GTR consists of particle size distributions that range from adiameter of 2 mm to 0.5 mm and are produced in a variety of waysincluding grinding methods such as cryogenic grinding. Micronized rubberpowder, or MRP, is termed as such because it generally contains asignificant fraction of particles less than 100 microns in size. MRP mayalso be produced by either ambient or cryogenic grinding methods.Powders such as GTR and MRP are commonly designated by their mesh size.For example, powders in the size range of 10-30 mesh generally areconsidered GTR, while 40-300 mesh materials generally are consideredMRP. GTR typically is less expensive than MRP because of the highermanufacturing cost required for making the smaller particles. Because ofthis cost difference, GTR generally is used instead of MRP, unless thespecific application requires properties than can only be achievedthrough the use of MRP. As noted previously, reclaimed elastomermaterials used to manufacture elastomer particles generally are obtainedfrom previously-manufactured products (e.g., used and unused vehicletires) and from vulcanized scrap generated during the manufacturingprocess (e.g., vulcanized scrap generated from the tire manufacturingprocess), and thus the reclaimed elastomer material is generallyvulcanized.

Vulcanized particles are relatively inert, i.e., the particles arenon-reactive with virgin matrix materials. As such, they are limited intheir use as a component in elastomer compositions because when added athigh levels, the resultant elastomer composition exhibits diminishedperformance characteristics. This limitation, however, can be eased bythe use of functionalized particles.

Vulcanized elastomer material can be functionalized through a variety ofprocesses. Broadly speaking, functionalization involves modifying thechemistry of the vulcanized particles. One such functionalizationprocess is devulcanization. Devulcanization processes are disclosed, forexample, in U.S. Pat. No. 5,770,632, U.S. Pat. No. 6,451,526 B1, U.S.Pat. No. 6,831,109 B1, European Patent Application No. 0 748 837 A1,European Patent Application No. 1 242 520 B1, European PatentApplication No. 0 690 091 A1 and U.S. Patent Application Publication No.2010/0317752. Generally speaking, devulcanization involves the chemical,thermal, and/or mechanical treatment of vulcanized elastomer to breakthe chemical crosslinks formed during the vulcanization process. Onedevulcanization process involves applying a chemical additive to thereclaimed vulcanized particles while the particles are under shearstresses. This type of functionalization is performed, for example, byLevgum, Ltd., having a principal place of business in Kanot, Israel. Analternate devulcanization process utilizes high temperatures as opposedto chemicals to break the chemical crosslinks. In these processes, theinput powder is reacted and generally converted into a spongy mass. Theresulting devulcanized (i.e., functionalized) material can then be usedin admixtures with virgin elastomeric materials. Previously, in terms ofreclaimed rubber powders, only GTR has been considered as a raw materialfor functionalization, for three reasons. First, the GTR is lower incost. Second, the resultant “spongy mass” functionalized material isidentical in appearance regardless of the particle size of the inputmaterial. Third, the assumption has been that, in a chemical, thermaland/or mechanical devulcanization process, the input particle size isirrelevant since the entire mass of the material is converted during thedevulcanization process. For example, in U.S. Pat. No. 6,831,109,vulcanized rubber in the form of crumb having a size of 0.5 to 5.0 mm orpieces having a thickness of up to 15 mm was devulcanized in a two rollmill.

While elastomer compositions comprising functionalized GTR exhibitimproved mechanical properties as compared to elastomer compositionscomprising vulcanized GTR, the use of functionalized GTR in admixturewith virgin material can still result in a reduction in the mechanicalproperties of the resulting elastomer formulations. It was assumedpreviously that elastomer compositions comprising functionalized GTR orfunctionalized MRP would exhibit comparable performance characteristicsirrespective of the size of the input functionalized particles.Specifically, the conventional assumption has been that elastomercompositions and other material compositions comprising functionalizedrubber powder of any particle size would exhibit diminished strength anddurability properties (e.g., measured through tensile strength tests) ascompared to those comprising virgin elastomer materials. Further, it hasbeen assumed that the functionalization process renders the particlesize of the input material irrelevant with respect to the finalproperties of admixed compositions.

Therefore, there is a long-felt but unresolved need for elastomercompositions that comprise reclaimed elastomer materials, but whichretain mechanical properties comparable to elastomer compositionscontaining no reclaimed material. The use of functionalized MRP can meetthis need.

SUMMARY

A method of functionalizing reclaimed elastomer material, the reclaimedelastomer material including an elastomer having intra-chain andinter-chain bonds, is provided wherein the method comprises:

subjecting particles of the reclaimed elastomer material to shear attemperatures less than 100° C. such that inter-chain bonds of thereclaimed elastomer material are cleaved;

wherein the particles of the reclaimed elastomer material have a size of40 mesh or smaller.

A functionalized reclaimed elastomer material made by a method as setforth above is also provided.

An elastomer compound is also provided which comprises:

uncured elastomer;

functionalized reclaimed elastomer material as set forth above;

a filler; and

a crosslinking agent.

An article of manufacture comprising a cross-linked elastomer compoundas set forth above is also provided.

These and other features of the present teachings are set forth herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing tensile strength as a function of elongationat break of an SBR/BR blend wherein data is shown for a controlcomprising no functionalized material and compositions comprisingfunctionalized material of differing particle size.

DETAILED DESCRIPTION

For the purpose of promoting an understanding of the principles of thepresent disclosure, reference will now be made to the embodimentsillustrated in the tables and attached exhibits, and specific languagewill be used to describe the same. It will, nevertheless, be understoodthat no limitation of the scope of the disclosure is thereby intended;any alterations and further modifications of the described orillustrated embodiments, and any further applications of the principlesof the disclosure as illustrated therein are contemplated as wouldnormally occur to one skilled in the art to which the disclosurerelates.

As used herein and recited in the attached exhibits, the term “PolyDyne”or “PD” refers to a brand name of vulcanized elastomer particles (e.g.,cured rubber particles, recycled rubber particles, ground tire rubber,GTR, micronized rubber powder, or MRP) produced by Lehigh Technologies,Inc. of Tucker, Ga. According to one embodiment, the particles describedherein are produced via a cryogenic grinding system described by U.S.Pat. No. 7,445,170, entitled Process and Apparatus for ManufacturingCrumb and Powder Rubber, and an impact mill as described by U.S. Pat.No. 7,861,958, entitled Conical-Shaped Impact Mill. In other embodimentsof the present disclosure, these micronized rubber powders are producedvia a variety of other known processes and techniques as will occur toone of ordinary skill in the art, and the powders used herein are notlimited to the specific cryogenic grinding processes described herein.

As also used herein and recited in the attached exhibits, “PD80”generally refers to a reclaimed elastomer material composition (i.e.,micronized rubber powder) conforming to conventional 80 mesh standards,“PD40” generally refers to MRP conforming to conventional 40 meshstandards, and so on. Thus, PD40, PD80, etc. are proprietary brand namesused to describe specific reclaimed elastomer material compositions(whether GTR or MRP) produced by Lehigh Technologies, Inc., which havepredetermined particle size distributions. As will be understood andappreciated, the specific formulations associated with PD40 or PD80 orany other formulation are presented purely for illustrative purposes andelastomeric compositions, reclaimed elastomer material compositions, orother elastomer formulations contemplated by the present disclosure arenot limited to the specific characteristics or features recited herein.

Further, as used herein, “functionalized” material generally refers tofunctionalized or devulcanized material made from micronized rubberpowders, as described herein above. In one embodiment, thisfunctionalized material is obtained from Levgum, Ltd., which as notedpreviously, has a principal place of business in Kanot, Israel. For theparticular experiments described herein, Levgum, Ltd. used GTR and MRPmanufactured by Lehigh Technologies, Inc., as the vulcanized particulatefeedstock. As will be understood and appreciated, the functionalizedmaterial obtained from Levgum, Ltd., is simply one type offunctionalized material that can be utilized within embodiments of thepresent formulations or compositions, and aspects of the presentdisclosure are not intended to be limited in any way to use of aspecific functionalized or devulcanized material.

As noted previously, it heretofore was assumed that elastomercompositions comprising functionalized material would exhibit diminishedperformance characteristics as compared to similar compositionsincluding no MRP, irrespective of the size of the functionalizedparticles. Put differently, it was assumed that elastomer compositionscomprising functionalized material made from 10 mesh, 20 mesh, 40 mesh,80 mesh (or virtually any other size) particles would exhibit similarmechanical properties as compared to each other, and that the propertieswould be diminished as compared to compositions comprising no MRP. Toconfirm this assumption and to identify and collect statistical measuresrelating to strength and other durability characteristics of suchelastomer compositions, sample elastomer formulations comprising variouspercentages of functionalized material were produced such that theirperformance characteristics could be tested and compared to each otherand to control samples comprising no MRP.

A method of functionalizing reclaimed elastomer material is provided.The reclaimed elastomer material includes an elastomer component havingintra-chain and inter-chain bonds. The method comprises subjectingparticles of the reclaimed elastomer material to shear at temperaturesless than 100° C. such that inter-chain bonds of the reclaimed elastomermaterial are cleaved wherein the particles of the reclaimed elastomermaterial have a size of 40 mesh or smaller.

According to some embodiments, the reclaimed elastomer material issubjected to shear by feeding the reclaimed elastomer material into thenip between first and second counter-rotating rolls, wherein the firstroll is rotating at a different speed than the second roll. According tosome embodiments, the rolls are maintained at a temperature of 50° C. orless while the reclaimed elastomer material is subjected to shear.According to some embodiments, the rolls are spaced at a distance of 0.1mm or less. According to some embodiments, the reclaimed elastomermaterial is passed through the rolls multiple times.

According to some embodiments, the particles of the reclaimed elastomermaterial have a size of 80 mesh or smaller. According to someembodiments, the particles of the reclaimed elastomer material aresubjected to shear at temperatures less than 50° C.

According to some embodiments, the reclaimed elastomer material issubjected to shear in the presence of a modifier which selectivelypromotes the cleavage of inter-chain bonds in the reclaimed elastomermaterial. According to some embodiments, the inter-chain bonds of thereclaimed elastomer material comprise C—S and S—S bonds and wherein theintra-chain bonds of the reclaimed elastomer material comprise C—C bondsand wherein the modifier selectively promotes the cleavage of theinter-chain C—S and S—S bonds compared to the intra-chain C—C bonds.According to some embodiments, the modifier comprises: a urea or ureaderivative of the formula

wherein R₁, R₂ and R₃ are each independently hydrogen or an organicradical; and a dicarboxylic acid with 2-8 carbon atoms in the mainchain. According to some embodiments, the molar ratio of the urea orurea derivative to the dicarboxylic acid can range from about 0.5:1 toabout 2.5:1. According to some embodiments, the urea or urea derivativeis urea and the dicarboxylic acid is selected from the group consistingof adipic acid, oxalic acid and sebacic acid.

Other known devulcanization agents can also be used as a modifier in theabove-described method. For example, according to some embodiment, thedevulcanization agents disclosed in European Patent Application No. 0690 091 A1 can be used as a modifier. These devulcanization agentscomprises a chemical mixture of a zinc salt of a thiocarbamate(zinc-dimethyldithiocarbamate) and 2-mercaptobenzothiazole, orderivatives thereof, in a molar ratio of 1:1 to 1:12. The chemicalmixture is preferably dispersed in a diol such as diethylene glycol andactivated by stearic acid, zinc oxide and sulfur.

According to some embodiments, the reclaimed elastomer material is madeby a cryogenic grinding process.

According to some embodiments, the reclaimed elastomer materialcomprises vehicle tire buffings. According to some embodiments, thereclaimed elastomer material comprises butadiene rubber (BR), naturalrubber (NR), a blend of NR and BR or a blend of styrene-butadiene rubber(SBR) and NR as an elastomer component.

A functionalized reclaimed elastomer material made by a method as setforth above is also provided.

An elastomer compound is also provided which comprises: uncuredelastomer; a functionalized reclaimed elastomer material as set forthabove; a filler; and a crosslinking agent. According to someembodiments, the particles of the reclaimed elastomer material have asize of 40 mesh or smaller. According to some embodiments, the particlesof the reclaimed elastomer material have a size of 50 mesh or smaller.According to some embodiments, the particles of the reclaimed elastomermaterial have a size of 80 mesh or smaller. According to someembodiments, the elastomer compound comprises between 3% and 30% byweight of the functionalized reclaimed elastomer material.

An article of manufacture comprising a cross-linked elastomer compoundas set forth above is also provided. According to some embodiments, thearticle of manufacture is a tire.

Experimental

The practice of this invention can be further understood by reference tothe following examples, which are provided by way of illustration onlyare not intended to be limiting.

Exemplary formulations of an SBR/BR elastomer blend formulationcomprising no functionalized material (control) as well as compositionscomprising functionalized material of differing particle size input areset forth in the following table.

TABLE 1 Exemplary SBR/BR Elastomer Blend Formulations Standard SBR/BRCompound 10% 10 10% 20 10% 40 10% 80 Control Mesh Mesh Mesh Mesh UnitsPHR PHR PHR PHR PHR ESBR1500 (Non-oil extended) 40.00 40.00 40.00 40.0040.00 Carbomix SBR BMB 1847K 67.50 67.50 67.50 67.50 67.50 High Cis PBR(CB 1220) 30.00 30.00 30.00 30.00 30.00 Functionalized 10 mesh 22.69Functionalized 20 mesh 22.69 Functionalized 40 mesh 22.69 Functionalized80 mesh 22.69 Nytex 4700 Process Oil 5.00 5.00 5.00 5.00 5.00 Struktol40MS 1.00 1.00 1.00 1.00 1.00 Alkyl Phenol Formaldehyde 3.00 3.00 3.003.00 3.00 Novalak Tack Resin N339 Carbon Black 42.50 42.50 42.50 42.5042.50 6PPD Antidegradant (PD-2) 2.00 2.23 2.23 2.23 2.23 Antioxidant DQ(TMQ) 1.00 1.12 1.12 1.12 1.12 Akrowax 5084 (Wax Blend) 2.00 2.23 2.232.23 2.23 Zinc Oxide Dispersion (85% 3.53 3.53 3.53 3.53 3.53 ZnO)Stearic Acid 2.00 2.00 2.00 2.00 2.00 TBBS 1.00 0.85 0.85 0.85 0.85 DPG0.10 0.10 0.10 0.10 0.10 Sulfur Dispersion (80% Sulfur) 2.75 3.16 3.163.16 3.16 Retarder CTP 0.10 0.10 0.10 0.10 0.10 Total PHR Finish Batch203.48 227.01 227.01 227.01 227.01The exemplary control formulation shown in the table above includes noMRP (either vulcanized or functionalized). When functionalized materialwas added to the composition of the exemplary control formulationaccording to the “over batch weight” addition method (as will beunderstood by one of ordinary skill in the art), the percentage of othercomposition materials was reduced accordingly in a conventional manner.

Specifically, other formulations as illustrated in the above table werealso tested, including those with 10% functionalized 10 mesh GTR, 10%functionalized 20 mesh GTR, 10% functionalized 40 mesh MRP, and 10%functionalized 80 mesh MRP. The 10, 20, 40 and 80 mesh materials weretaken from the same lot of truck tread buffings commercially availablein North America. The 10 mesh material was screened from the buffingsusing a standard RoTap technique. The 20, 40 and 80 mesh materials arecommercially available from Lehigh Technologies, Tucker, Ga. under thedesignations PD20, PD40 and PD80, respectively. Functionalization wasperformed by Levgum, Ltd., Kanot, Israel. The reclaimed elastomermaterial was functionalized by passing the material through a two rollmill having a 0.1 mm nip. The rolls were cooled during processing. Therolls had a diameter of 130 mm with one roll rotating at 25 rpm and oneroll rotating at 12.5 rpm (roll ratio of 2:1). The use of a two-rollmill to produce shear is exemplary only and other methods of subjectingthe reclaimed elastomer to shear at low temperatures (e.g., 100° C. orless or 50° C. or less) may by employed.

The formulation mixing and compounding process was performed usingstandard industry practice with one exception—the functionalizedmaterial was added to the mix in the first mixing pass along with thecarbon black. The formulations were cured for 20 minutes at 320° F. Thetensile testing method used was ASTM D412-98a (2002). As will beunderstood by one of ordinary skill in the art, the sample controlformulation described in the above table, as well as the resultingformulations in which functionalized material is added to the control,were used purely for illustrative purposes, and are not intended to belimiting of the elastomer compositions or formulations that could beused in connection with aspects of the present disclosure.

Tests were performed on the cured samples to measure various physicalproperties of the samples. Table 2 below includes experimental resultsrelating to tensile strength testing of the cured elastomer compositionsamples.

TABLE 2 Tensile Testing Data for SBR/BR Elastomer Blend FormulationTensile Strength (MPa) Elongation (%) Relative Quality Control 18.3 6611 10% F10 15.1 520 0.65 10% F20 16.0 559 0.74 10% F40 16.3 599 0.81 10%F80 17.3 613 0.88For instance, tensile strength data, as per test method ASTM D 412 andmeasured in MPa, was collected for various samples. Surprisingly, thesamples comprising smaller particle size functionalized MRP demonstratedhigher quality mechanical properties as compared to the samplescomprising larger particle size functionalized GTR. As shown in Table 2,elastomeric composition samples comprising 10% 20 mesh functionalizedGTR (10% F20) had an average tensile strength of 16.0 MPa. Samplescomprising 10% 10 mesh functionalized GTR (10% F10), however, only hadan average tensile strength of 15.1 MPa, which is approximately 5.79%lower. Likewise, samples comprising 10% 80 mesh functionalized MRP (10%F80) had an average tensile strength of 17.3 MPa, whereas samplescomprising 10% 40 mesh MRP (10% F40) had an average tensile strength of16.3 MPa (i.e., approximately 5.95% lower). Generally, testing showedthat elastomer compositions comprising functionalized MRP of aparticular mesh size exhibit tensile strength approximately 6% greaterthan compositions comprising functionalized powder one mesh size larger(for samples comprising 10, 20, 40, and 80 mesh functionalized GTR/MRP).

The data shown in Table 2 above also illustrates that samples comprisingfunctionalized MRP of smaller mesh size demonstrate superior elongationas compared to samples with larger mesh functionalized GTR. For example,as shown in the table above and in FIG. 2, the 80 mesh samples exhibitedelongation of 613%, whereas the 40 mesh samples exhibited elongation of599%. Likewise, the 20 mesh samples exhibited elongation of 559%,whereas the 10 mesh samples exhibited elongation of 520%. Generally, forthe mesh sizes tested, samples exhibited improved elongation when thesample comprised functionalized material with smaller mesh size input.

Further, the table above also shows the relative quality of the testedsamples. The relative quality was determined by taking the product oftensile strength and elongation for the respective sample and dividingthat quantity by the product of the tensile strength and elongation forthe control material. Generally, the higher the relative quality, themore applications the material can be used in. For example, as therelative quality approaches approximately 0.9, the material can beconsidered as similar enough to the control compound to be used as asubstitute in high performance tire tread applications. Only thefunctionalized 80 mesh MRP approaches this level of 0.9 relativequality.

Again, these findings demonstrate that the mechanical properties of thesamples improve as the size of the functionalized MRP particles getssmaller. The findings relating to improved tensile strengthcharacteristics and improved elongation characteristics of elastomercompositions including smaller mesh size functionalized MRP (as detailedin FIG. 1) are unexpected and advantageous for several reasons.Specifically, as previously noted, adding reclaimed material to anelastomer composition reduces the composition's overall production cost;however, it was believed that inclusion of functionalized material,regardless of particle size input, would diminish the materialproperties of the composition. As outlined above and in FIG. 1,elastomer compositions comprising functionalized MRP with smallerdiameter (e.g., 40 mesh and 80 mesh) exhibit increased tensile strengthand elongation as compared to compositions comprising functionalized GTRwith larger diameter (e.g., 20 mesh or 10 mesh), thus potentiallyenabling their use in certain elastomer compositions and making suchcompositions suitable for applications that were previously consideredunsuitable.

The foregoing description of the exemplary embodiments has beenpresented only for the purposes of illustration and description and isnot intended to be exhaustive or to limit the inventions to the preciseforms disclosed. Many modifications and variations are possible in lightof the above teaching.

The embodiments were chosen and described in order to explain theprinciples of the inventions and their practical application so as toenable others skilled in the art to utilize the inventions and variousembodiments and with various modifications as are suited to theparticular use contemplated. Alternative embodiments will becomeapparent to those skilled in the art to which the present inventionspertain without departing from their spirit and scope.

What is claimed is:
 1. An elastomer compound comprising: uncuredelastomer; functionalized reclaimed elastomer material, wherein thereclaimed elastomer material is functionalized by subjecting particlesof the reclaimed elastomer material comprising a size less than or equalto 40 mesh to shear at temperatures less than 100° C. such thatinter-chain bonds of the reclaimed elastomer material are cleaved; afiller; and a crosslinking agent.
 2. The elastomer compound of claim 1,wherein the particles of the reclaimed elastomer material comprise asize less than or equal to 50 mesh.
 3. The elastomer compound of claim1, wherein the particles of the reclaimed elastomer material comprise asize less than or equal to 80 mesh.
 4. The elastomer compound of claim1, wherein the elastomer compound comprises between 3% and 30% by weightof the functionalized reclaimed elastomer material.
 5. An article ofmanufacture comprising a cross-linked elastomer compound as set forth inclaim
 1. 6. The article of manufacture of claim 5, wherein the articleof manufacture is a tire.
 7. A functionalized reclaimed elastomermaterial made by the method comprising subjecting particles of thereclaimed elastomer material to shear at temperatures less than 100° C.such that inter-chain bonds of the reclaimed elastomer material arecleaved, wherein the particles of the reclaimed elastomer material havea size less than or equal to 40 mesh.